This research is an investigation of the biosynthesis of estrogens and other steroid hormones, and the interrelationships between human development and steroid hormones. It aims also to develop useful biochemical and analytical methods of clinical applicability. Our immediate objectives are: 1) to elucidate the steric, kinetic, and electronic mechanisms of aromatization and lyase reaction by human steroid hormones synthesizing systems, 2) to isolate and characterize placental aromatases and to determine the molecular structures, 3) to elucidate pathway(s) through which hydroxylated steroid hormones are formed, 4) to identify natural steroids and their conjugates and study the mode of conjugation and excretion, 5) to elucidate steroid configurations and conformations, 6) to develop active-site directed affinity labeling steroids and 7) to develop rapid and simple clinical assays of estrogens. The methods involve synthesis of steroids with and without deuterium, tritium, carbon-13, carbon-14 and oxygen-18 labels at stereoselective and/or regiospecific positions, conformational analysis by X-ray crystallography and spectroscopy, chemical and biochemical distribution analysis of isotopes, incubations with various enzyme preparations of combinations of regio- and stereoselectively labeled steroids, and analyses of the products by physico-chemical or radio-immunotechnology. A neutral resin, steady state distribution machine, chromatographies, nmr and mass spectrometry are used for the isolation and characterization of steroids and their conjugates. Solubilization, purification and physico-chemical identification of membrane-bound proteins are used for isolation and structure determination of the enzyme systems.